Why does the enzyme trypsin get deactivated when introduced in the gastric juice of the stomach? the optimum ph for trypsin is about 8.0, which is the ph of the intestine, whereas the ph of gastric juice is 1.5 - 2.0, which is highly acidic. the optimum ph for trypsin is about 2.0, which is the ph of the intestine, whereas the ph of gastric juice is 8.0, which is highly alkaline. the optimum temperature for trypsin is about 98.6°f (37°c), which is the temperature of the intestine; whereas the temperature of gastric juice is 392 - 482°f (200°c - 250°c).